1. Field of the Invention
The invention relates to a device for the collection of liquids, such as whole blood from which serum is to be extracted. The device is vented to the atmosphere and therefore relies primarily on the hydrostatic or other pressure of the liquid being collected to fill the device. The device also has the capability for serum separation and dispensing, following the collection.
2. State of the Prior Art
Of the many devices available to provide blood serum for analysis, the one which has become the norm is the evacuated container. This is simply a partially evacuated glass tube openable at one end except for a septum placed there. One improvement over such an evacuated container which is particularly useful comprises such a glass tube with a movable plug contained within the tube. The plug is preferably a silica gel, with or without a plastic cup-like mandrel positioned with its open end pointed to the septum. By reason of the vacuum, collected blood is easily drawn into the container. The container is then spun about a centrifuge axis adjacent to the septum end, and the gel by reason of its selected specific gravity works up to the serum-cell interface where it plugs the container against remixing of the serum and cells. An example of such a container but without the mandrel is shown in U.S. Pat. No. 3,852,194.
Although such a device is useful in separating the serum from the cells, it has not avoided the transfer difficulties by which the separated serum is obtained. That is, after centrifuging, the serum is commonly poured off into yet another container for the desired clinical testing. All such transfer operations are time consuming, requiring either hand processing or complicated, expensive automatic handling. Furthermore, whenever there is a transfer of a liquid sample to a separate, open container, the sample is aerated and CO.sub.2 loss or gain can occur. There is also the danger of improper transfer, either by the use of the wrong container, by the improper patient labeling of the new container, or by both. Still further, contamination of the serum by foreign materials can occur, including for example, contamination by blood cells collected at the septum-container interface prior to centrifuging, a condition known as "blood-ring contamination."
Still other drawbacks concerning evacuated containers are that the rapid intake tends to cause hemolysis by reason of the high shear rate, the vacuum can cause collapse of the patient's vein, and occasionally the containers become "flat," i.e., they lose their vacuum. In such a case of a "flat" container, the broken seal is generally insufficient to create a truly vented configuration, so that the hydrostatic pressure of the veins from which the blood is drawn encounters back pressure, and the rate of fill is insufficient. When the container is formed from solid glass, it is not possible prior to actual use to determine the loss of vacuum merely by visual inspection, and the result is that the patient has to wait while the technician looks for a new, hopefully evacuated, container.
On the other hand, previous vented containers by their nature have been prone to blood spillage, and any spillage or leakage of blood can in turn infect the technician or operator. Furthermore, vented containers generally have not provided the rate of fill characteristic of an evacuated container in which the initial vacuum has been maintained. Thus, vented containers have not been a successful replacement for evacuated containers.
Devices have been developed such as those shown in U.S. Pat. No. 3,433,216, for reusing "flat" blood collection devices. Specifically, the sterilized "flat" collector is placed within an encompassing compartment which is vented and which has a telescoping portion, and a passageway is provided between the two compartments. By closing the vent of the outer compartment, and moving the telescoping portion, a vacuum is thus created, either before or during filling of the collection device. However, the outermost compartment is not designed to function as a blood storage or capture means, and the entire combination makes no provision for a dispensing operation after blood serum separation is complete. Furthermore, there is no provision for a capillary filling of the original blood collection device.
Capillary draws have been used to collect blood, using either one or more simple capillary tubes as in U.S. Pat. No. 3,645,252, or a capillary tube which is connected to and permits flow of the blood into a large container of the type shown, for example, in U.S. Pat. No. 3,640,267. The devices of the latter patent have been designed solely for non-venous collecting, and are not suitable for serum separation in the same container.
Mild obstructions have been placed in blood collecting devices for various purposes other than for creating a capillary effect at the obstruction to fill the container more rapidly. For example, the pipette shown in U.S. Pat. No. 3,741,732 has capillary flow along its entire length, and the obstruction by its hydrophobic nature is designed to terminate rather than assist flow. In the syringe disclosed in U.S. Pat. No. 2,941,869, a coiled wire is disposed in a tube solely to hemolyze the blood flowing past it. Nowhere is capillary flow discussed.
Blood flow devices having capillary restrictions at a portion intermediate the ends thereof have been constructed not for the purpose of collecting blood and for separating serum, but rather for blood cell counting, as shown for example, in U.S. Pat. Nos. 2,369,577; 2,779,232; 2,807,416 and 2,875,666. These devices are not intended for, nor are they capable of, use as serum collectors and separators as there is no provision, for example, for means for controlling flow out of both of the ends of the devices. Instead the flow is commonly gravity or diffusion flow, there being no need to otherwise control it.
Flexible containers have been used to collect whole blood, and by reason of their flexibility, they may have capillary passageways somewhere defined when the walls are collapsed. However, the collapsed wall condition is designed not to fill the containers by capillary action, but rather either to create a vacuum which causes filling of the container, as shown for example in U.S. Pat. No. 3,513,829, or to indicate whether desired arterial blood as opposed to undesired venous blood is being collected, as shown for example in U.S. Pat. No. 3,785,367.
U.S. Pat. No. 3,867,923 is representative of blood collection bags which are completely collapsed along their entire length, and which therefore provide a capillary passageway their entire length. However, such devices lose their effective capillary as soon as blood enters. Because they are not vented to the atmosphere, they require the patient's blood pressure to expand the device into its full volume. No additional means can be applied to assist in the filling of the bag.
Patents relating generally to the background of blood collection include for example U.S. Pat. No. 3,610,226.